In a typical inkjet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol, a polyhydric alcohol or mixtures thereof.
An ink-recording element typically comprises a support having on at least one surface thereof an ink-receiving or image-forming layer, and includes those intended for reflection viewing, which have an opaque support, and those intended for viewing by transmitted light, which have a transparent support.
In order to achieve and maintain high quality images on such an image-recording element, the recording element must exhibit no banding, bleed, coalescence, or cracking in inked areas; exhibit the ability to absorb large amounts of ink and dry quickly to avoid blocking; exhibit high optical densities in the printed areas; exhibit freedom from differential gloss; exhibit high levels of image fastness to avoid fade from contact with water or radiation by daylight, tungsten light, or fluorescent light or exposure to gaseous pollutants; and exhibit excellent adhesive strength so that delamination does not occur.
Titanium dioxide, zinc oxide, silica, and polymeric beads such as cross-linked poly(methyl methacrylate) or polystyrene beads have been used in the receiving layer or layers used in ink recording elements for the purposes of contributing to the non-blocking characteristics of the recording elements or to control the smudge resistance thereof.
U.S. Pat. No. 6,447,114 issued Sep. 10, 2002 to Sunderrajan et al., titled “Inkjet Printing Method,” uses inorganic pigments in a porous overcoat. The amount of inorganic pigment used may range from about 50 to about 95% of the image-receiving layer. Such particles include silica, alumina, calcium carbonate, modified kaolin clay, montmorillinite clay, hydrotactite clay, and laponite clay.
U.S. Patent Publication No. 2003/0112311 A1 published Jun. 19, 2003 by Naik et al., titled “Topcoat Compositions, Substrates Containing A Topcoat Derived Therefrom, and Methods of Preparing the Same” discloses an ink-receptive composition comprising a filler, binder such as polyvinyl alcohol, cationic polymer.
U.S. Pat. No 6,341,560 issued Jan. 29, 2002 to Shah et al., titled “Imaging And Printing Methods Using Clay-containing Fluid Receiving Element,” discloses a lithographic imaging member that is prepared by applying an ink-jetable fluid to a fluid-receiving element that includes a clay-containing fluid-receiving surface layer. Useful clays that are used are either synthetic or naturally occurring materials, including but not limited to kaolin (aluminum silicate hydroxide) and many other clays such as serpentine, montmorillonites, illites, glauconite, chlorite, vermiculites, bauxites, attapulgites, sepiolites, palygorskites, corrensites, allophanes, imoglites, and others.
Aluminosilicates are known in various forms. For example aluminosilicate polymers are known in fiber form, such as imogolite. Imogolite is a filamentary, tubular and crystallized aluminosilicate, present in the impure natural state in volcanic ashes and certain soils; it was described for the first time by Wada in Journal of Soil Sci. 1979, 30(2), 347–355. In comparison, allophanes are in the form of substantially amorphous particles.
Naturally occurring allophane is a series name used to describe clay-sized, short-range ordered aluminosilicates associated with the weathering of volcanic ashes and glasses. Such natural allophane commonly occurs as very small rings or spheres having diameters of approximately 35–50 Å (3.5 to 5.0 nm). This morphology is characteristic of allophane, and can be used in its identification. Naturally occurring allophanes have a composition of approximately Al2Si2O5.nH2O. Some degree of variability in the Si:Al ratios is present. Wada reports Si:Al ratios varying from about 1:1 to 2:1. Because of the exceedingly small particle size of allophane and the intimate contact between allophane and other clays (such as smectites, imogolite, or non-crystalline Fe and Al oxides and hydroxides and silica) in the soil, it has proven very difficult to accurately determine the composition of naturally occurring allophane. Allophane usually gives weak XRD peaks at 2.25 and 3.3 Å. Identification is commonly made by infrared analyses or based on transmission electron morphology.
A limited amount of isomorphous substitution occurs in natural allophane. The most common type is the substitution of Fe for Al. In some cases, the color of this natural allophane is dark yellow due to the presence of Fe3+, the presence of which can interfere with making Raman spectrum of the natural allophane due to the presence of this Fe3+ traces (fluoresence under the laser excitation).
Little permanent charge is typically present in natural allophane. The majority of the charge is variable charge, and both cation and anion exchange capacities exist, with the relative amounts depending on the pH and ionic strength of the soil chemical environment.
Synthetic allophane, like natural allophane, is also a substantially amorphous material having weak XRD signals. The particle size (average diameter) typically is in the range of about 4 to 5.5 nm. Due to their small size, it is difficult to obtain a photo of a single unit of synthetic allophane, but they commonly appear substantially spherical, which spheres are usually hollow. The zeta potential of synthetic allophane is positive, which is in the range of other pure alumina materials. There is data supporting the chemical anisotropy of synthetic allophane, with aluminols at the outer surface, silanols wrapping the inner surface. Aluminosilicate polymers, in spherical particle form, that can be described as synthetic allophanes are disclosed in U.S. Pat. No. 6,254,845 issued Jul. 3, 2001 to Ohashi et al., titled “Synthesis Method Of Spherical Hollow Aluminosilicate Cluster,” which patent describes an improved method for preparing hollow spheres of amorphous aluminosilicate polymer similar to natural allophane. This patent also refers to Wada, S., Nendo Kagaku (Journal of the Clay Science Soc. of Japan), Vol. 25, No. 2, pp. 53–60, 1985) for another synthesis of amorphous aluminosilicate superfine particles. The aluminosilicate polymers in U.S. Pat. No. 6,254,845 to Ohashi et al. are within a range of 1–10 nm, shaped as hollow spheres, and are observed to form hollow spherical silicate “clusters” or aggregates in which pores are formed. The patent to Ohashi et al. states that powder X-ray diffraction reveals two broad peaks close to 27° and 40° at 2θ on the Cu—Kα line, which correspond to a non-crystalline (substantially amorphous) structure and which is characteristic of spherical particles referred to as allophane. In addition, observations under a transmission microscope reveal a state in which hollow spherical particles with diameters of 3–5 nm are evenly distributed.
Regarding the Al/Si ratio, it is believed that sufficient silanol group is needed to form an homogeneous layer of silicate on the face of the proto gibbsite sheet, sufficient to curl this protogibbsite sheet and finally allowing a closo structure to be obtained. The Al/Si ratio, therefore, has to be in the range 1 to 4.
Two types of synthetic allophane, referred to as hybrid and classical, are disclosed in French Applications FR 0209086 and FR 0209085 filed on Jul. 18, 2002. Hybrid Synthetic allophanes show the same fingerprints as classical allophane with some additional bands due to the presence of organic groups.
As indicated above, synthetic and natural allophane are generally non-crystalline materials, which include both amorphous and short-range ordered materials such as microcrystalline materials. Amorphous materials are at the opposite extreme from crystalline materials—they do not have a regularly repeating structure, even on a molecular scale. Their compositions may be regular or, as is more commonly the case, they may have a large degree of variability. They do not produce XRD peaks. Since the term amorphous is sometime applied to materials that are truly amorphous, like volcanic glass, the term x-ray amorphous or simply non-crystalline can be used to describe allophanes and other short-range ordered materials that may show weak XRD peaks and hence not completely amorphous. Such aluminosilicate materials will be referred to herein as substantially amorphous. Short-range ordered materials can sometimes be identified by XRD or selective dissolution in conjunction with differential XRD.
While a wide variety of different types of image recording elements for use with ink printing are known, there are many unsolved problems in the art and many deficiencies in the known products, which have severely limited their commercial usefulness. A major challenge in the design of an image-recording element is to provide heat and humidity keeping, especially for swellable, non-porous recording elements.
It is an object of this invention to provide a multilayer ink recording element that has excellent image quality and improved humidity keeping.
Still another object of the invention is to provide a printing method using the above-described element.